to make the sauce, in an extra-small saucepan,stir together the sugar,sesame oil,soy sauce,and water.
bring to a boil over medium heat
give the cornstarch a last stir,then swirl it in.
stir the sauce for about 20 seconds,untill it has thickened.
transfer to a small bowl and let cool to roon temparature,about 15 minutes;you should have 1/4 cup